RunScript is supposed to return the exit code from the script. If
CreateProcess fails, however, it calls SetLastError, and then returns
FALSE. This is wrong. It should probably return -1, as it does in the
other failure cases.

(Unfortunately, for various non-technical reasons, I can't create a
patch right now).

Cheers,
Roger.

P.S. Yeah, I'm finally getting around to changing the hooks to not block
the UI...